Electrical stimulation is an effective therapy for a variety of conditions and diseases that adversely affect patient health. For example, electrical stimulation has been effective in alleviating chronic pain, movement disorders, gastrointestinal disorders, and pelvic floor disorders. Spinal cord stimulation systems have been found to provide relief for chronic pain. Deep brain stimulation can be effective in treatment of movement disorders such as Parkinson's disease, as well as other neurological disorders such as epilepsy. Stimulation of the gastrointestinal tract can be effective in alleviating gastroparesis and obesity. Stimulation of the pelvic floor can be effective in alleviating urinary incontinence, fecal incontinence, pelvic pain, and sexual dysfunction.
Typically, electrical stimulation is delivered by an implantable pulse generator that is chronically implanted within the patient. One or more leads extending from the implantable pulse generator carry electrodes for delivery of stimulation energy to a target tissue or nerve site. Unfortunately, some patients may not respond to stimulation therapy. For this reason, a physician often prescribes a course of trial or “screening” stimulation to evaluate the likely efficacy of electrical stimulation therapy for the patient. In particular, an external trial stimulator is used to evaluate the efficacy of stimulation before implanting a chronic stimulator. A chronic stimulator typically requires surgical implantation and may be implanted for several years.
An external trial stimulator is ordinarily electrically coupled to one or more implanted leads through a percutaneous extension. The trial stimulator may be carried by the patient, e.g., at the waist. The physician penetrates through the skin and tunnels the leads to a target site. Upon connection of the leads to the external trial stimulator, trial stimulation is activated to emulate the therapy delivered by a chronically implanted stimulator. Although the trial stimulator may only be used for a short time, e.g., a period of hours, days or weeks, the patient and physician are able to determine if the stimulation therapy is effective in alleviating the symptoms.
If the therapy is successful, the patient may undergo surgery to implant a chronic stimulator. If the trial therapy is unsuccessful, the physician may alter the trial stimulation, try another type of stimulation therapy, or abandon stimulation therapy. In the case of an unsuccessful therapy, the use of the external trial stimulator is beneficial in avoiding the need to implant and then explant a chronically implanted device. In this way, the time, labor, patient risk, and patient discomfort associated with surgical implantation and explantation can be avoided. On the other hand, successful trial therapy provides heightened confidence in the efficacy of chronic implantation, and may reveal desirable stimulation parameter settings to be programmed into the implantable stimulator.